The need to store digital files, documents, pictures, images and other data continues to increase rapidly. In connection with the electronic storage of data, various data storage systems have been devised for the rapid and secure storage of large amounts of data. Such systems may include one or a plurality of storage devices that are used in a coordinated fashion. Systems in which data can be distributed across multiple storage devices such that data will not be irretrievably lost if one of the storage devices (or in some cases, more than one storage device) fails are also available. Systems that coordinate operation of a number of individual storage devices can also provide improved data access and/or storage times. Examples of systems that can provide such advantages can be found in the various RAID (redundant array of independent disks) levels that have been developed. Whether implemented using one or a plurality of storage devices, the storage provided by a data storage system can be treated as one or more storage volumes.
In today's storage world, many data storage systems are based on either Fibre Channel (FC) or Serial Attached SCSI (SAS) interfaces to disk enclosures. Fibre Channel disk enclosures are typically based on Arbitrated Loop (FC-AL) and optionally include Fibre Channel Loop Switches. In either case, the FC-AL addressing scheme usually dictates enclosure identification. Soft FC addressing is convenient, but is considered too loose for most system administrators. Hard FC addressing is less convenient to configure, but is easier to manage, especially in larger configurations. In many cases, the user must configure an enclosure's hard FC address-range through the use of a thumb-wheel or other mechanical interface. The thumb-wheel identifies the enclosure (via its mechanical display), and controls the FC addresses of the disks and SCSI Enclosure Services (SES) target within that enclosure. Since users use mechanical switches to assign IDs, two or more enclosures may end up with the same enclosure ID. One or more enclosures will then have to be assigned a different ID automatically. Additionally, there is no easy way to show a user which enclosures have duplicate IDs.
The SAS standard is quite different with respect to device addressing. Specifically, all SAS devices are addressed via their 64-bit World Wide Name (WWN). There is no equivalent in SAS to the simple scalar (0, 1, 2, . . . , n) used by FC or parallel SCSI to address drives. The WWN can hardly be considered user friendly for device identification. Since the WWN is used, there is no need for a thumb-wheel, or equivalent mechanical interface. Moreover, providing the user with one is artificial and could be misleading to the user trying to find the SAS device. Mechanical thumb-wheel switches could be used in SAS, but possible duplicates would still have to be handled. For both FC and SAS it seems that there is still a need for a method of identifying enclosures and devices contained therein.